There are two means of delimiting identifiers in T-SQL:
1) Using Square Brackets e.g. [MyColumn] this is proprietary to T-SQL
2) The ANSI standard way using double quotes, “MyColumn”
But delimiting is only required when an identifier does not conform to the rules for formatting identifiers. These rules are that the first character must be an upper or lower case letter, underscore, @ sign or number sign. The identifier cannot be a reserved word, no embedded spaces and no supplementary characters. If the identifier does not meet these requirements it must be delimited.
Delving into Exam 70-461, the following quote from Georg Cantor is lain out at the very beginning to show the genesis of set theory and by extension SQL. Georg Cantor was the creator of mathematical set theory and defined a set as follows:
By a set we mean any collection M into a whole of definite, distinct objects m (which are called the elements of M) of our perception or of our thought.
There are more details on Cantor in this excellent documentary by Marcus De Sautoy: